In its function as an ITRS Combination
Centre, DGFI is in charge with the computation of an ITRF2008 solution. The
computation methodology of DGFI is based on the combination of datum-free
normal equations (weekly or session data sets, respectively) of station
positions and Earth orientation parameters (EOP) from the geodetic space techniques
DORIS, GPS, SLR and VLBI. In this paper we focus on
the DORIS part within the ITRF2008
computations. We present results obtained from the analysis of the DORIS time series for station positions,
network translation and scale parameters, as well as for the terrestrial pole
coordinates. The submissions to ITRF2008 benefit from improved analysis
strategies of the seven contributing IDS analysis centres and from a
combination of the weekly solutions of station positions and polar motion. The
results show an improvement by a factor of two compared to past DORIS data submitted to ITRF2005, which
has been evaluated by investigating the repeatabilities of position time
series. The DORIS position time series were analysed
w.r.t. discontinuities and other non-linear effects such as seasonal
variations. About 40 discontinuities have been identified which have been
compared with the results of an earlier study. Within the inter-technique
combination we focus on the DORIS contribution to the integration of the different space
geodetic observations and on a comparison of the geodetic local ties with the
space geodetic solutions. Results are given for the 41 co-location sites
between DORIS and GPS.

Every three years the IAU Working Group
on Cartographic Coordinates and Rotational Elements revises tables giving the
directions of the poles of rotation and the prime meridians of the planets,
satellites, minor planets, and comets. This report takes into account the IAU
Working Group for Planetary System Nomenclature (WGPSN) and the IAU Committee
on Small Body Nomenclature (CSBN) definition of dwarf planets, introduces
improved values for the pole and rotation rate of Mercury, returns the rotation
rate of Jupiter to a previous value, introduces improved values for the
rotation of five satellites of Saturn, and adds the equatorial radius of the
Sun for comparison. It also adds or updates size and shape information for the
Earth, Mars' satellites Deimos and Phobos, the four Galilean satellites of
Jupiter, and 22 satellites of Saturn. Pole, rotation, and size information has
been added for the asteroids (21) Lutetia, (511) Davida, and (2867) .teins.
Pole and rotation information has been added for (2) Pallas and (21) Lutetia.
Pole and rotation and mean radius information has been added for (1) Ceres.
Pole information has been updated for (4) Vesta. The high precision realization
for the pole and rotation rate of the Moon is updated. Alternative orientation
models for Mars, Jupiter, and Saturn are noted. The Working Group also
reaffirms that once an observable feature at a defined longitude is chosen, a
longitude definition origin should not change except under unusual
circumstances. It is also noted that alternative coordinate systems may exist
for various (e.g. dynamical) purposes, but specific cartographic coordinate
system information continues to be recommended for each body. The Working Group
elaborates on its purpose, and also announces its plans to occasionally provide
limited updates to its recommendations via its website, in order to address
community needs for some updates more often than every 3 years. Brief
recommendations are also made to the general planetary community regarding the
need for controlled products, and improved or consensus rotation models for
Mars, Jupiter, and Saturn.

We present a systematic survey of
numerical geodynamo simulations where the inner core is allowed to
differentially rotate in the longitudinal direction with respect to the mantle.
We focus on the long-term behaviour of inner core rotation, on timescales much
longer than the overturn time of the fluid outer core, including the steady
component of rotation. The inner core is subject to viscous and magnetic
torques exerted by the fluid outer core, and a gravitational restoring torque
exerted by the mantle. We show that the rate of steady inner core rotation is
limited by the differential rotation between spherical surfaces that the
convective dynamics can sustain across the fluid outer core. We further show
that this differential rotation is determined by a torque balance between the
resistive Lorentz force and the Coriolis force on spherical surfaces within the
fluid core. We derive a scaling law on the basis of this equilibrium suggesting
that the ratio of the steady inner core rotation to typical angular velocity
within the fluid core should be proportional to the square root of the Ekman
number, in agreement with our numerical results. The addition of gravitational
coupling does not alter this scaling, though it further reduces the amplitude
of inner core rotation. In contrast, the long-term fluctuations in inner core
rotation remain proportional to the fluid core angular velocity, with no
apparent dependency on the Ekman number. If the same torque balance pertains to
the Earth's core conditions, the inner core rotation then consists in a very
slow super rotation of a few degrees per million years, superimposed over large
fluctuations (at about a tenth of a degree per year). This suggests that the
present-day seismically inferred inner core rotation is a fragment of a time-varying
signal, rather than a steady super rotation. For the inner core rotation
fluctuations not to cause excessive variations in the length-of-day, the
strength of the gravitational coupling between the inner core and the mantle
must be smaller than previously published values. We finally explore how the
torque balance which we observe in our models could be altered in planetary
cores, yielding possibly larger values of the steady rotation.

Context. Grain growth in circumstellar
disks is expected to be the first step towards the formation of planetary
systems. There is now evidence for grain growth in several disks around young
stars.

Aims: Radially resolved images of grain growth in
circumstellar disks are believed to be a powerful tool to constrain the dust
evolution models and the initial stage for the formation of planets. In this
paper we attempt to provide these constraints for the disk surrounding the
young star CQ Tau. This system was already suggested from previous studies to
host a population of grains grown to large sizes.

Methods: We present new high angular resolution
(0.3"-0.9") observations at wavelengths from 850 ?m to 3.6 cm
obtained at the SMA, IRAM-PdBI and NRAO-VLA interferometers. We perform a
combined analysis of the spectral energy distribution and of the
high-resolution images at different wavelengths using a model to describe the
dust thermal emission from the circumstellar disk. We include a prescription
for the gas emission from the inner regions of the system.

Results: We detect the presence of evolved dust by
constraining the disk averaged dust opacity coefficient b (computed between 1.3 and 7 mm) to
be 0.6±0.1. This confirms the earlier suggestions that the disk contains dust
grains grown to significant sizes and puts this on firmer grounds by tightly
constraining the gas contamination to the observed fluxes at mm-cm wavelengths.
We report some evidence of radial variations in dust properties, but current
resolution and sensitivity are still too low for definitive results.

We evaluate the orbital evolution and
several plausible origin scenarios for the mutually inclined orbits of u And c and d. These two planets have
orbital elements that oscillate with large amplitudes and lie close to the
stability boundary. This configuration, and in particular the observed mutual
inclination, demands an explanation. The planetary system may be influenced by
a nearby low-mass star, u And B, which could perturb the planetary orbits, but we find it cannot
modify two coplanar orbits into the observed mutual inclination of 30°.
However, it could incite ejections or collisions between planetary companions
that subsequently raise the mutual inclination to >30°. Our simulated systems
with large mutual inclinations tend to be further from the stability boundary
than u And, but we
are able to produce similar systems. We conclude that scattering is a plausible
mechanism to explain the observed orbits of u And c and d, but we cannot determine whether the
scattering was caused by instabilities among the planets themselves or by
perturbations from u And B. We also develop a procedure to quantitatively
compare numerous properties of the observed system to our numerical models.
Although we only implement this procedure to ? And, it may be applied to any
exoplanetary system.

The hot Jupiter HD 209458b was observed
during primary transit at 3.6, 4.5, 5.8 and 8.0 mm using the Infrared Array Camera
(IRAC) on the Spitzer Space Telescope. We describe the procedures we adopted to
correct for the systematic effects present in the IRAC data and the subsequent
analysis. The light curves were fitted including limb-darkening effects and
fitted using Markov Chain Monte Carlo and prayer-bead Monte Carlo techniques, obtaining almost
identical results. The final depth measurements obtained by a combined Markov
Chain Monte Carlo fit are at 3.6 mm, 1.469 ± 0.013 and 1.448 ± 0.013 per cent; at 4.5 mm, 1.478 ± 0.017 per cent; at 5.8 mm, 1.549 ± 0.015 per cent; and at
8.0 mm, 1.535 ±
0.011 per cent. Our results clearly indicate the presence of water in the
planetary atmosphere. Our broad-band photometric measurements with IRAC prevent
us from determining the additional presence of other molecules such as CO, CO2
and methane for which spectroscopy is needed. While water vapour with a mixing
ratio of ? combined
with thermal profiles retrieved from the day side may provide a very good fit
to our observations, this data set alone is unable to resolve completely the degeneracy
between water abundance and atmospheric thermal profile.

We present photometry of the giant
extrasolar planet WASP-4b at 3.6 and 4.5 mm taken with the Infrared Array Camera on board the
Spitzer Space Telescope as part of Spitzer's extended warm mission. We find
secondary eclipse depths of 0.319% ± 0.031% and 0.343% ± 0.027% for the 3.6 and
4.5 mm bands,
respectively, and show model emission spectra and pressure-temperature profiles
for the planetary atmosphere. These eclipse depths are well fit by model
emission spectra with water and other molecules in absorption, similar to those
used for TrES-3 and HD 189733b. Depending on our choice of model, these results
indicate that this planet has either a weak dayside temperature inversion or no
inversion at all. The absence of a strong thermal inversion on this highly
irradiated planet is contrary to the idea that highly irradiated planets are
expected to have inversions, perhaps due the presence of an unknown absorber in
the upper atmosphere. This result might be explained by the modestly enhanced
activity level of WASP-4b's G7V host star, which could increase the amount of
UV flux received by the planet, therefore reducing the abundance of the unknown
stratospheric absorber in the planetary atmosphere as suggested in Knutson et
al. We also find no evidence for an offset in the timing of the secondary
eclipse and place a 2s upper limit on |ecos w| of 0.0024, which constrains the range of tidal heating
models that could explain this planet's inflated radius.

Context. During the past few years,
eclipse exoplanet spectroscopy has enabled the detection of H2O, CH4,
CO2, and CO in the atmosphere of hot Jupiters and Neptunes. At the
same time, ~40 likely large terrestrial planets are announced or confirmed. Two
of these are transiting, and another is deemed habitable. Therefore the
potential for eclipse spectroscopy of terrestrial planets with the James Webb
Space Telescope (JWST) has become an active field of study.

Aims: We aim to extensively explore the parameter space
(type of stars, planet orbital periods, planet types, and
instruments/wavelengths) in terms of signal-to-noise ratio (S/N) of the
detection of spectroscopic features with the JWST. We also wish to confront the
information on the S/N to the likelihood of occurring targets.

Methods: We used analytic formula and model data for both
the astrophysical scene and the instrument to plot S/N contour maps, while
indicating how the S/N scales with the fixed parameters. We systematically
compare stellar photon noise-only plots with plots that include detailed
instrumental and zodiacal noises. The likelihood of targets is based on both
model and catalog star populations of the solar neighborhood

Results: The 9.6 mm ozone band is detectable (S/N = 3) with JWST, for a
warm super earth 6.7 pc away, using ~2% of the 5-year nominal mission time
(summing observations, M4 V and lighter host star for primary eclipses, M5 V
for secondary). If every star up to this mass limit and distance were to host a
habitable planet, there would be statistically a little under one eclipsing
case. We also show that detection in transmission of the 2.05 mm CO2 feature on the 6.5
MEarth exoplanet GJ 1214 b is feasible with the Hubble Space
Telescope (HST). For the low and the high bounds of the likely atmospheric mean
molecular weight, just one eclipse or the whole HST yearly visibility window
(107 days) is required.

Conclusions: It is critical to investigate systematic noises
resulting from co-adding hours-long observations separated by tens of days,
over a 5 year span. It is also critical to perform a dedicated characterization
of the instruments, currently in integration phase. The census of nearby
transiting habitable planets must be complete before JWST's science operations
start.

We observed comet C/2007 N3 (Lulin)
twice on UT 2009 January 28, using the UV grism of the Ultraviolet and Optical
Telescope on board the Swift gamma-ray burst space observatory. Grism
spectroscopy provides spatially resolved spectroscopy over large apertures for
faint objects. We developed a novel methodology to analyze grism observations
of comets, and applied a Haser comet model to extract production rates of OH,
CS, NH, CN, C3, C2, and dust. The water production rates
retrieved from two visits on this date were 6.7 ± 0.7 and 7.9 ± 0.7 ×1028
molecules s.1, respectively. Jets were sought (but not found) in the
white-light and "OH" images reported here, suggesting that the jets
reported by Knight & Schleicher are unique to CN. Based on the abundances
of its carbon-bearing species, comet Lulin is "typical" (i.e.,
not "depleted") in its composition.

We report the discovery by the CoRoT
space mission of a transiting brown dwarf orbiting a F7V star with an orbital
period of 3.06 days. CoRoT-15b has a radius of 1.12+0.30-0.15
{R}Jup and a mass of 63.3 ± 4.1 {M}Jup, and is thus the
second transiting companion lying in the theoretical mass domain of brown
dwarfs. CoRoT-15b is either very young or inflated compared to standard
evolution models, a situation similar to that of M-dwarf stars orbiting close
to solar-type stars. Spectroscopic constraints and an analysis of the
lightcurve imply a spin period in the range 2.9-3.1 days for the central star,
which is compatible with a double-synchronisation of the system.

Issues related to long timescale
instability in the Earth's rotation, named True Polar Wander (TPW), have
continuously been debated, after the pioneering works of the sixties. We show
ice age TPW results from a newly developed compressible model, based on the
numerical integration in the radial variable of the momentum and Poisson
equations and on the contour integration in the Laplace domain which allows us to deal with
the non-modal contribution from continuous radial rheological variations. We
thus fully exploit the long term behaviour of the Earth's rotation and we
quantify the effects of the compressible rheology, compared to the widely used
incompressible one. We discuss the so-called `traditional approach' to the
Earth's rotation developed during the eighties and nineties, both for ice age
and mantle convection TPW and we explain within this approach the sensitivity
of TWP predictions to the elastic and
viscoelastic rheologies of the lithosphere. We agree on the necessity to
include the effects of the non-hydrostatic bulge from mantle convection to
obtain realistic ice age TPW rates in the lower mantle viscosity range [1021,
1022] Pa s, as first indicated by Mitrovica et al.
Their analysis represents a first attempt to couple the effects on TPW from
mantle convection and glacial forcing, by including the non-hydrostatic bulge
due to mantle convection but not the other time-dependent driving terms. This
partial coupling freezes in space the non-hydrostatic contribution due to
mantle convection, thus damping the present-day ice age TPW and forcing the
axis of instantaneous rotation to come back to its initial position when ice
ages started as discussed in Mitrovica et al. We also describe a
peculiar behavior of the new ice age TPW predictions exhibiting a dampened
pendulum motion, with the axis of instantaneous rotation overcrossing the
position it had before ice ages started. We argue that a viscoelastic rather
than elastic lithosphere should be adopted in the modelling of TPW although, on
the time of ice ages, it is difficult to disentangle the effects of
lithospheric rheology and of mantle convection. We discuss the implication of
self-consistent convection calculations of the non-hydrostatic contribution and
its impact on the long term Earth's rotation stability during ice ages. The ice
age TPW cannot account for more than 70 per cent of the observed one, at least
for lower mantle viscosities lower than 1022 Pa s: mantle convection
must therefore contribute to the observed TPW.

We present a 4-planet Keplerian fit for the radial velocity
curve of the F8V star ? Andromeda, indicating the presence of a fourth planet
in the system. We detect an additional fifth coherent signal in the radial
velocity curve which we attribute to stellar activity. The discovery of a new
planet around u Andromedae makes this system the fifth to contain, at least, four
planets. These four planets have minimum masses of 0.69, 1.98, 4.13 and 1.06 MJup
and orbital periods of 4.62, 241.26, 1276.46 and 3848.9 days, respectively. We
have numerically integrated the orbital solution for these four planets and
find that the system is stable for at least 10 Myr. The orbit of the fourth
planet coincides with an island of stability reported by Rivera &
Haghighipour (2007, MNRAS, 374, 599). We find that the characteristics of the
new fourth planet are very similar to those of Jupiter and that the planets in
this system have very strong interactions with each other. As previously found,
u And-b and u And-c are in apsidal alignment,
while the orbit of the new planet (u And-e) is close to an external 3:1 resonance with u And-c.

We measure secondary eclipses of the hot giant exoplanets
CoRoT-1 at 3.6 and 4.5 mm, and CoRoT-2 at 3.6 mm, both using Warm Spitzer. We find that the Warm Spitzer
mission is working very well for exoplanet science. For consistency of our
analysis we also re-analyze archival cryogenic Spitzer data for secondary
eclipses of CoRoT-2 at 4.5 and 8 mm. We compare the total data for both planets,
including optical eclipse measurements by the CoRoT mission, and ground-based
eclipse measurements at 2 mm, to existing models. Both planets exhibit stronger
eclipses at 4.5 than at 3.6 mm, which is often indicative of an atmospheric temperature
inversion. The spectrum of CoRoT-1 is best reproduced by a 2460 K blackbody,
due either to a high altitude layer that strongly absorbs stellar irradiance,
or an isothermal region in the planetary atmosphere. The spectrum of CoRoT-2 is
unusual because the 8 mm contrast is anomalously low. Non-inverted atmospheres could
potentially produce the CoRoT-2 spectrum if the planet exhibits line emission
from CO at 4.5 mm, caused by tidal-induced mass loss. However, the viability of that
hypothesis is questionable because the emitting region cannot be more than
about 30% larger than the planet's transit radius, based on the ingress and
egress times at eclipse. An alternative possibility to account for the spectrum
of CoRoT-2 is an additional opacity source that acts strongly at wavelengths
less than 5 mm, heating the
upper atmosphere while allowing the deeper atmosphere seen at 8 mm to remain cooler. We obtain a
similar result as Gillon et al. for the phase of the secondary eclipse
of CoRoT-2, implying an eccentric orbit with e cos(w) = .0.0030 ± 0.0004.

Suitably generalized, ocean tide models can be used to
determine the oceans' response to atmospheric pressure forcing; but the huge
range of spatial and temporal scales of that forcing limits the relevance of
state-of-the-art tide modeling techniques, like data assimilation, for such
determinations. With an interest in its effects on Earth's rotation, in 1998 I
employed a generalized but non-assimilating spherical harmonic tide model to
determine the oceanic response to pressure forcing, however restricting its
application to time scales exceeding a few days. This article revisits that
spherical harmonic model in an attempt to improve its rotational predictions of
short-period tides. We find that increasing the resolution of the model ocean
does not by itself affect the tidal solution much, but varying the model's
frictional parameters can produce diurnal tides whose effects on Earth's polar
motion are similar to those of a variety of other ocean tide models. Such an
improved model will allow our calculations of the oceans' dynamic response to
pressure forcing, and the effects of that response on Earth's rotation, to be
extended down to diurnal time scales.

Since giant planets scatter
planetesimals within a few tidal radii of their orbits, the locations of
existing planetesimal belts indicate regions where giant planet formation
failed in bygone protostellar disks. Infrared observations of circumstellar
dust produced by colliding planetesimals are therefore powerful probes of the
formation histories of known planets. Here we present new Spitzer infrared
spectrograph (IRS) spectrophotometry of 111 solar-type stars, including 105 planet hosts.
Our observations reveal 11 debris disks, including two previously undetected
debris disks orbiting HD 108874 and HD 130322. Combining the 32 mm spectrophotometry with previously
published MIPS photometry, we find that the majority of debris disks around solar-type
stars have temperatures in the range 60 <~ Tdust <~ 100 K.
Assuming a dust temperature Tdust = 70 K, which is representative of
the nine debris disks detected by both IRS and MIPS, debris rings surrounding Sun-like
stars orbit between 15 and 240 AU depending on the mean particle size. Our
observations imply that the planets detected by radial-velocity searches formed
within 240 AU of their parent stars. If any of the debris disks studied here
have mostly large, blackbody emitting grains, their companion giant planets
must have formed in a narrow region between the ice line and 15 AU.

Context. Stellar noise produced by oscillations, granulation
phenomena (granulation, mesogranulation, and supergranulation), and activity
affects radial velocity measurements. The signature of the corresponding effect
in radial velocity is small, around the meter-per-second, but already too large
for the detection of Earth-mass planets in habitable zones.

Aims: We address the important role played by observational
strategies in averaging out the radial velocity signature of stellar noise. We
also derive the planetary mass detection limits expected in the presence of
stellar noise.

Methods: We start with HARPS asteroseismology measurements
for four stars (b Hyi, a Cen A, m Ara, and t Ceti) available in the ESO archive and very precise measurements of a Cen B. This sample covers different
spectral types from G2 to K1 and different evolutionary stages, from subgiant
to dwarf stars. Since data span between 5 and 8 days, only stellar noise
sources with timescales shorter than this time span will be extracted from
these observations. Therefore, we are able to study oscillation modes and
granulation phenomena without being significantly affected by activity noise
present on longer timescales. For those five stars, we generate synthetic
radial velocity measurements after fitting the corresponding models of stellar
noise in Fourier space. These measurements allow us to study the radial
velocity variation due to stellar noise for different observational strategies
as well as the corresponding planetary mass detection limits.

Results: Applying three measurements per night of 10 min
exposure each, 2 h apart, seems to most efficiently average out the stellar
noise considered. For quiet K1V stars such as a Cen B, this strategy allows us to
detect planets of about three times the mass of Earth with an orbital period of
200 days, corresponding to the habitable zone of the star. Moreover, our
simulations suggest that planets smaller than typically 5 MEarth can
be detected with HARPS over a wide range of separations around most non-active
solar-type dwarfs. Since activity is not yet included in our simulation, these
detection limits correspond to a case, which exists, where the host star has
few magnetic features and stellar noise is dominated by oscillation modes and
granulation phenomena. For our star sample, a trend between spectral type and
surface gravity and the level of radial velocity variation is also identified
by our simulations

We present the first results from long-term photometric observations
carried out with the INTA-CAB 50-cm telescope in a fully robotic mode. The data
belong to an ongoing programme for the photometric follow up of known
transiting close-in giant planets. We describe the techniques used to generate
differential light curves of the programme stars and discuss the photometric
performance obtained over the first year of operation.

The Trojan asteroids, a very substantial population of
primitive bodies trapped in Jupiter's stable Lagrange regions, remain quite
poorly understood. Because they occupy these orbits, the physical properties of
Trojans provide a unique perspective on the chemical and dynamical processes
that shaped the Solar System. The current study was therefore undertaken to
investigate surface compositions of these objects. We present 66 new
near-infrared (NIR; 0.7-2.5 ?m) spectra of 58 Trojan asteroids, including
members of both the leading and trailing swarms. We also include in the
analysis previously published NIR spectra of 13 Trojans (3 of which overlap with
the new sample). This data set permits not only a direct search for
compositional signatures, but also a search for patterns that may reveal clues
to the origin of the Trojans. We do not report any confirmed absorption
features in the new spectra. Analysis of the spectral slopes, however, reveals
an interesting bimodality among the NIR data. The two spectral groups
identified appear to be equally abundant in the leading and trailing swarms.
The spectral groups are not a result of family membership; they occur in the
background, non-family population. The average albedos of the two groups are
the same within uncertainties (0.051 ± 0.016 and 0.055 ± 0.016). No
correlations between spectral slope and any other physical or orbital parameter
are detected, with the exception of a possible weak correlation with
inclination among the less-red spectral group. The NIR spectral groups are
consistent with a similar bimodality previously suggested among visible colors
and spectra. Synthesizing the present results with previously published
properties of Trojans, we conclude that the two spectral groups represent
objects with different intrinsic compositions. We further suggest that whereas
the less-red group originated near Jupiter or in the main asteroid belt, the
redder spectral group originated farther out in the Solar System. If this
suggestion is correct, the Trojan swarms offer the most readily accessible
large reservoir of Kuiper Belt material as well as a unique reservoir for the
study of material from the middle part of the solar nebula.

We have performed extensive simulations
to explore the possibility of detecting eclipses and transits of close,
substellar and planetary companions to white dwarfs in WASP (the UK Wide-Angle
Search for Planets) light curves. Our simulations cover companions ~0.3 < Rpl
< 12 REarth and orbital periods 2 < P < 15 d, equivalent to
orbital radii 0.003 < a < 0.1 au. For Gaussian random noise, WASP is
sensitive to transits by companions as small as the Moon orbiting a V ~= 12
white dwarf. For fainter white dwarfs, WASP is sensitive to increasingly larger
radius bodies. However, in the presence of correlated noise structure in the
light curves, the sensitivity drops, although Earth-sized companions remain
detectable, in principle, even in low signal-to-noise data. Mars-sized, and
even Mercury-sized, bodies yield reasonable detection rates in high-quality
light curves with little residual noise. We searched for eclipses and transit
signals in long-term light curves of a sample of 194 white dwarfs resulting
from a cross-correlation of the McCook & Sion catalogue and the WASP
archive. No evidence for eclipsing or transiting substellar and planetary
companions was found. We used this non-detection and results from our simulations
to place tentative upper limits to the frequency of such objects in close
orbits at white dwarfs. While only weak limits can be placed on the likely
frequency of Earth-sized or smaller companions, brown dwarfs and gas giants
(radius ≈ RJup) with periods <0.1-0.2 d must certainly be
rare (<10 per cent). More stringent constraints likely require significantly
larger white dwarf samples, higher observing cadence and continuous coverage.
The short duration of eclipses and transits of white dwarfs compared to the
cadence of WASP observations appears to be one of the main factors limiting the
detection rate in a survey optimized for planetary transits of main-sequence
stars.

Among the 48 known multiplanetary systems, some are in
mean-motion resonances (in most cases in the 2:1 mean-motion resonance).
Although until now no extrasolar planetary systems have been found in a 1:1
mean-motion resonance, many studies are dealing with this configuration.
Besides the well-known motion of the Trojan asteroids, further possibilities
exist for stable configurations of planets or satellites in a 1:1 resonance.
For one thing, we can find so-called exchange orbits in our Solar system (Janus
and Epimetheus), where both Saturnian moons exchange the values of their
semi-major axes (exchange-a configuration) when approaching each other. In addition,
we can also find similar behaviour for two planets on orbits with the same
semi-major axis, but with different eccentricities; here an exchange of
eccentricities takes place (exchange-e configuration). In this work we focused
on the second possibility and performed a parameter study by varying the
initial conditions (mass and eccentricity) of two planets on exchange-e orbits.
By means of an extensive numerical study, we can find a wide variety of initial
conditions leading to long-term stable orbits.

We report the results of dynamical simulations, covering Gyr
timescales, of fictitious Scattered Disk Objects as a follow-up to an earlier
study. Our dynamical model is similar in that it does not include external
agents like passing stars or the Galactic tide. Only the four giant planets are
explicitly treated as perturbers. We analyze the random-walk behavior of the
inverse semi-major axis by means of a simplified circular restricted 3-body
problem as an approximate analogue. Our results concerning the role of resonant
effects and the transfer efficiency into the orbital energy domain of the inner
Oort Cloud are in broad agreement with the earlier papers, and we confirm the
important role of external objects (with perihelia beyond Neptune's orbit) in
feeding the Oort Cloud. We estimate the efficiency of this transfer to be even
somewhat higher than previously found.

The CoRoT exoplanet science team
announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a
V = 12.9 mag F6 dwarf star (M *= 1.27±0.05 MSun, R*= 1.37±0.03 RSun, Teff =
6440±120 K), with an orbital period of P = 2.994329±0.000011 days and
semi-major axis a = 0.0436±0.005 AU. The detection of part of the radial
velocity anomaly caused by the Rossiter-McLaughlin effect shows that the
transit-like events detected by CoRoT are caused by a planet-sized transiting
object in a prograde orbit. The relatively high projected rotational velocity
of the star (v sin i = 40±5 km s-1) places CoRoT-11 among the most
rapidly rotating planet host stars discovered so far. With a planetary mass of
Mp = 2.33±0.34 MJup and radius Rp =1.43±0.03 RJup,
the resulting mean density of CoRoT-11b (rp = 0.99±0.15 g/cm3) can
be explained with a model for an inflated hydrogen-planet with a solar
composition and a high level of energy dissipation in its interior.

Because the planets of a system form in a flattened disk,
they are expected to share similar orbital inclinations at the end of their
formation. The high-precision photometric monitoring of stars known to host a
transiting planet could thus reveal the transits of one or more other planets.
We investigate here the potential of this approach for the M dwarf GJ 1214 that
hosts a transiting super-Earth. For this system, we infer the transit
probabilities as a function of orbital periods. Using Monte-Carlo simulations
we address both the cases for fully coplanar and for non-coplanar orbits, with
three different choices of inclinations distribution for the non-coplanar case.
GJ 1214 reveals to be a very promising target for the considered approach.
Because of its small size, a ground-based photometric monitoring of this star
could detect the transit of a habitable planet as small as the Earth, while a
space-based monitoring could detect any transiting habitable planet down to the
size of Mars. The mass measurement of such a small planet would be out of reach
for current facilities, but we emphasize that a planet mass would not be needed
to confirm the planetary nature of the transiting object. Furthermore, the
radius measurement combined with theoretical arguments would help us to
constrain the structure of the planet.

We perform a detailed investigation into the disruption of
central cusps via the transfer of energy from sinking massive objects. Constant
density inner regions form at the radius where the enclosed mass approximately
matches the mass of the infalling body. We explore parameter space using
numerical simulations and give an empirical relation for the size of the
resulting core within structures that have different initial cusp slopes. We
find that infalling bodies always stall at the edge of these newly formed
cores, experiencing no dynamical friction over many dynamical times. As
applications, we consider the resulting decrease in the dark matter
annihilation flux due to centrally destroyed cusps, and we present a new theory
for the formation of close binary nuclei.the "stalled binary" model.
We focus on one particularly interesting binary nucleus system, the dwarf
spheroidal galaxy VCC 128 which is dark matter dominated at all radii. We show
that its nuclei would rapidly coalesce within a few million years if it has a
central dark matter cusp slope steeper than r -1. However, if its
initial dark matter cusp is slightly shallower than a logslope of -0.75 at
~0.1% of the virial radius, then the sinking nuclei naturally create a core
equal to their observed separation and stall. This is close to the logslope
measured in a recent billion particle cold dark matter halo simulation.

Gorshkov, V.L., 2010, "Study of
the interannual variations of the Earth's rotation," Solar System
Research,44, 487-497.

In this work we investigate the variations of the Earth's
rotation in the interval of periods from 2 to 8 years using the longest
available observational series obtained both by means of astrometry and space
geodesy. We found an abrupt change of the variation pattern in the middle of
the 1980s, when classical ground-based astrometric facilities for studying the
Earth Rotation Parameters (ERP) were replaced with space geodesy methods.
Variations with a 6-year periodicity and ~0.2-ms amplitude practically disappeared
(space geodesy instruments did not detect these variations right from the
start), but the 2- to 4-year periodicities increased in amplitude and began to
dominate in this frequency range under consideration. In this study, we analyze
some possible excitation sources and possible causes of the change in the
variability pattern.

The Markov chain Monte Carlo (MCMC) method is a powerful technique for
facilitating Bayesian non-linear model fitting. In many cases, the MCMC exploration of the parameter space
is very inefficient, because the model parameters are highly correlated.
Differential evolution MCMC is one technique that addresses this problem by employing
multiple parallel chains. We present a new method that automatically achieves
efficient MCMC sampling in highly correlated parameter spaces, which does not require
additional chains to accomplish this. It was designed to work with an existing
hybrid MCMC (HMCMC) algorithm, which incorporates
parallel tempering, simulated annealing and genetic cross-over operations.
These features, together with the new correlated parameter sampler, greatly
facilitate the detection of a global minimum in c2. The new HMCMC algorithm is very
general in scope. Two tests of the algorithm are described employing (a)
exoplanet precision radial velocity (RV) data and (b) simulated space
astrometry data. The latter test explores the accuracy of parameter estimates
obtained with the Bayesian HMCMC algorithm on the assumed astrometric noise.

Context. The small radius and high
density of CoRoT-7b implies that this transiting planet belongs to a different
species than all transiting planets previously found. Current models suggest
that this is the first transiting rocky planet found outside the solar system.
Given that the planet orbits a solar-like star at a distance of only 4.5 R *, it is expected that material
released from its surface may then form an exosphere.

Aims: We constrain
the properties of the exosphere by observing the planet in- and out-of-transit.
Detecting the exosphere of CoRoT-7b would for the first time allow us to study
the material originating in the surface of a rocky extrasolar planet. We scan
the entire optical spectrum for any lines originating from the planet, focusing
particularly on spectral lines such as those detected in Mercury and Io in our
solar system.

Methods: Since lines originating in the exosphere are
expected to be narrow, we observed CoRoT-7b at high resolution with UVES on the
VLT. By subtracting the two spectra from each other, we search for emission and
absorption lines originating in the exosphere of CoRoT-7b.

Results: In the first step, we focus
on Ca I, Ca II, and Na, because these lines have been detected in Mercury. Since
the signal-to-noise ratio (S/N) of the spectra is as high as 300, we derive
firm upper limits for the flux-range between 1.6 ×10-18 and 3.2 ×10-18 W m-2. For CaO, we find an upper
limit of 10-17 W m-2. We also search for emission lines originating
in the plasma torus fed by volcanic activity and derive upper limits for these
lines. In the whole spectrum we finally try to identify other lines originating
in the planet.

Conclusions: Except for CaO, the
upper limits derived correspond to 2-6×0-6 L*, demonstrating the capability of
UVES to detect very weak lines. Our observations certainly exclude the extreme
interpretations of data for CoRoT-7b, such as an exosphere that emits 2000
times as brightly as Mercury.

Standard maximum-likelihood estimators for binary-star and
exoplanet eccentricities are biased high, in the sense that the estimated
eccentricity tends to be larger than the true eccentricity. As with most
non-trivial observables, a simple histogram of estimated eccentricities is not
a good estimate of the true eccentricity distribution. Here, we develop and
test a hierarchical probabilistic method for performing the relevant
meta-analysis, that is, inferring the true eccentricity distribution, taking as
input the likelihood functions for the individual star eccentricities, or
samplings of the posterior probability distributions for the eccentricities
(under a given, uninformative prior). The method is a simple implementation of
a hierarchical Bayesian model; it can also be seen as a kind of heteroscedastic
deconvolution. It can be applied to any quantity measured with finite
precision.other orbital parameters, or indeed any astronomical measurements of
any kind, including magnitudes, distances, or photometric redshifts.so long as
the measurements have been communicated as a likelihood function or a posterior
sampling.

We report the discovery of HD 156668 b, an extrasolar planet
with a minimum mass of MPsin i = 4.15 MEarth. This planet
was discovered through Keplerian modeling of precise radial velocities from
Keck-HIRES and is the second super-Earth to emerge from the NASA-UC Eta-Earth
Survey. The best-fit orbit is consistent with circular and has a period of P =
4.6455 days. The Doppler semi-amplitude of this planet, K = 1.89 m s.1,
is among the lowest ever detected, on par with the detection of GJ 581 e using
HARPS. A longer period (P ≈ 2.3 years), low-amplitude signal of unknown
origin was also detected in the radial velocities and was filtered out of the
data while fitting the short-period planet. Additional data are required to
determine if the long-period signal is due to a second planet, stellar
activity, or another source. Photometric observations using the Automated
Photometric Telescopes at Fairborn Observatory show that HD 156668 (an old,
quiet K3 dwarf) is photometrically constant over the radial velocity period to
0.1 mmag, supporting the existence of the planet. No transits were detected
down to a photometric limit of ~3 mmag, ruling out transiting planets dominated
by extremely bloated atmospheres, but not precluding a transiting solid/liquid
planet with a modest atmosphere.

Three transiting exoplanet candidate
stars were discovered in a ground-based photometric survey prior to the launch
of NASA's Kepler mission. Kepler observations of them were obtained during
Quarter 1 of the Kepler mission. All three stars are faint by radial velocity
follow-up standards, so we have examined these candidates with regard to
eliminating false positives and providing high confidence exoplanet selection.
We present a first attempt to exclude false positives for this set of faint
stars without high-resolution radial velocity analysis. This method of
exoplanet confirmation will form a large part of the Kepler mission follow-up
for Jupiter-sized exoplanet candidates orbiting faint stars. Using the Kepler
light curves and pixel data, as well as medium-resolution reconnaissance
spectroscopy and speckle imaging, we find that two of our candidates are binary
stars. One consists of a late-F star with an early M companion, while the other
is a K0 star plus a late M-dwarf/brown dwarf in a 19 day elliptical orbit. The
third candidate (BOKS-1) is an r = 15 G8V star hosting a newly discovered
exoplanet with a radius of 1.12 RJupiter in a 3.9 day orbit.

Hu, R., 2010, "Transport of the
First Rocks of the Solar System by X-winds," The Astrophysical Journal,725, 1421-1428.

It has been suggested that
chondrules and calcium-aluminum-rich inclusions (CAIs) were formed at the inner
edge of the protoplanetary disk and then entrained in magnetocentrifugal
X-winds. We study trajectories of such solid bodies with the consideration of
the central star gravity, the protoplanetary disk gravity, and the gas drag of
the wind. The efficiency of the gas drag depends on a parameter ?, which is the
product of the solid body size and density. We find that the gravity of the
protoplanetary disk has a non-negligible effect on the trajectories. If a solid
body re-enters the flared disk, the re-entering radius depends on the stellar
magnetic dipole moment, the disk's gravity, the parameter h, and the initial launching angle.
The disk's gravity can make the re-entering radius lower by up to 30%. We find
a threshold h, denoted as ht , for any particular configuration
of the X-wind, below which the solid bodies will be expelled from the planetary
system. ht sensitively depends on the initial
launching angle, and also depends on the mass of the disk. Only the solid
bodies with an h larger than but very close to ht can be launched to a re-entering
radius larger than 1 AU. This size-sorting effect may explain why chondrules
come with a narrow range of sizes within each chondritic class. In general, the
size distributions of CAIs and chondrules in chondrites can be determined from
the initial size distribution as well as the distribution over the initial
launching angle.

We discuss the effect
of the earth rotation on the two-triad interaction and the oceanic energy
distribution processes that occur between five coupled internal gravity waves.
The system we study is a two-triad test wave system consisting of an initial
wave of the tidal M2 frequency interacting with four recipient waves
forming two resonant triads. It is shown that the general mechanism of an
arbitrarily large number of internal wave interactions can be described by three
classes of interactions which we call the sum, middle and difference
interaction classes. The four latitude singularities are distinguished for the
particular case of five interacting waves and all three classes of resonant
interactions are studied separately at those critical values. It is shown that
the sum and difference interaction classes represent the latitude-inferior and
latitude-predominant classes respectively. The phenomenon of coalescence of the
middle and difference interaction classes is observed along latitude 48.25° N.
It shown that at this value of latitude, the coalescence phenomenon provides
the analogy between rotating and reflecting internal waves from slopes.

At wide separations, planetary-mass and brown dwarf
companions to solar-type stars occupy a curious region of parameter space not
obviously linked to binary star formation or solar system scale planet
formation. These companions provide insight into the extreme case of companion
formation (either binary or planetary), and due to their relative ease of
observation when compared to close companions, they offer a useful template for
our expectations of more typical planets. We present the results from an
adaptive optics imaging survey for wide (~50-500 AU) companions to solar-type
stars in Upper Scorpius. We report one new discovery of a ~14 MJ
companion around GSC 06214.00210and confirm that the candidate planetary-mass
companion 1RXS J160929.1.210524 detected by Lafreniè et al. is in fact
comoving with its primary star. In our survey, these two detections correspond
to ~4% of solar-type stars having companions in the 6-20 MJ mass and
~200-500 AU separation range. This figure is higher than would be expected if
brown dwarfs and planetary-mass companions were drawn from an extrapolation of
the binary mass function. Finally, we discuss implications for the formation of
these objects.

We report on the
discovery and the Rossiter-McLaughlin (R-M) effect of Kepler-8b, a transiting
planet identified by the NASA Kepler Mission. Kepler photometry and Keck-HIRES
radial velocities yield the radius and mass of the planet around this F8IV
subgiant host star. The planet has a radius RP= 1.419 RJ and
a mass MP= 0.60 MJ, yielding a density of 0.26 g cm-3,
one of the lowest planetary densities known. The orbital period is P = 3.523
days and the orbital semimajor axis is 0.0483+0.0006-0.0012
AU. The star has a large rotational vsin i of 10.5 ± 0.7 km s-1and
is relatively faint (V »13.89 mag); both properties are
deleterious to precise Doppler measurements. The velocities are indeed noisy,
with scatter of 30 m s-1, but exhibit a period and phase that are
consistent with those implied by transit photometry. We securely detect the R-M
effect, confirming the planet's existence and establishing its orbit as
prograde. We measure an inclination between the projected planetary orbital
axis and the projected stellar rotation axis of l= -26fdg4 ± 10fdg1, indicating a
significant inclination of the planetary orbit. R-M measurements of a large
sample of transiting planets from Kepler will provide a statistically robust
measure of the true distribution of spin-orbit orientations for hot Jupiters
around F and early G stars.

The large number of exoplanets found to orbit their host
stars in very close orbits have significantly advanced our understanding of the
planetary formation process. It is now widely accepted that such short-period
planets cannot have formed in situ, but rather must have migrated to their
current orbits from a formation location much farther from their host star. In
the late stages of planetary formation, once the gas in the protoplanetary disk
has dissipated and migration has halted, gas giants orbiting in the inner disk
regions will excite planetesimals and planetary embryos, resulting in an
increased rate of orbital crossings and large impacts. We present the results
of dynamical simulations for planetesimal evolution in this later stage of
planet formation. We find that a mechanism is revealed by which the
collision-merger of planetary embryos can kick terrestrial planets directly
into orbits extremely close to their parent stars.

The abundance of exoplanets with orbits smaller than that of
Mercury most likely implies that there are exoplanets exposed to a
quasiparallel stellar-wind magnetic field. Many of the generic features of
stellar-wind interaction depend on the existence of a non-zero perpendicular
interplanetary magnetic field component. However, for closer orbits the
perpendicular component becomes smaller and smaller. The resulting
quasiparallel interplanetary magnetic field may imply new types of
magnetospheres and interactions not seen in the solar system. We simulate the
Venus-like interaction between a supersonic stellar wind and an Earth-sized,
unmagnetized terrestrial planet with ionosphere, orbiting a Sun-like star at
0.2 AU. The importance of a quasiparallel stellar-wind interaction is then
studied by comparing three simulation runs with different angles between
stellar wind direction and interplanetary magnetic field. The plasma simulation
code is a hybrid code, representing ions as particles and electrons as a
massless, charge-neutralizing adiabatic fluid. Apart from being able to observe
generic features of supersonic stellar-wind interaction we observe the
following changes and trends when reducing the angle between stellar wind and
interplanetary magnetic field 1) that a large part of the bow shock is replaced
by an unstable quasiparallel bow shock; 2) weakening magnetic draping and
pile-up; 3) the creation of a second, flanking current sheet due to the need
for the interplanetary magnetic field lines to connect to almost antiparallel
draped field lines; 4) stellar wind reaching deeper into the dayside
ionosphere; and 5) a decreasing ionospheric mass loss. The speed of the last
two trends seems to accelerate at low angles.

Kashi, A., Soker, N., 2011, "The
outcome of the protoplanetary disk of very massive stars," New
Astronomy,16, 27-32.

We suggest that planets, brown dwarfs, and even low mass
stars can be formed by fragmentation of protoplanetary disks around very
massive stars (M >~ 100 MSun). We discuss how fragmentation
conditions make the formation of very massive planetary systems around very
massive stars favorable. Such planetary systems are likely to be composed of
brown dwarfs and low mass stars of .0.1.0.3 MSun, at orbital
separations of ~ few ×100.104 AU. In particular, scaling from
solar-like stars suggests that hundreds of Mercury-like planets might orbit
very massive stars at ~103 AU where conditions might favor liquid
water. Such fragmentation objects can be excellent targets for the James Webb
Space Telescope and other large telescopes working in the IR bands. We predict
that deep observations of very massive stars would reveal these fragmentation
objects, orbiting in the same orbital plane in cases where there are more than
one object.

The stability in the sense of Lagrange of the
Sun-Jupiter-Saturn system and 47 UMa system with respect to masses on a time
scale of 106 years was studied using the method of averaging and
numerical methods. When the masses of Jupiter and Saturn increase by 20 times
(approximately, more accurate value depends on a time-scale of stable motion),
these planets can have close approaches. Close approaches appear when analyzing
osculating elements; they are absent in the mean elements. A similar situation
takes place in the case of 47 UMa and other exoplanetary systems. The study of
Lagrange stability with respect to masses allows us to obtain upper limits for
masses of extrasolar planets.

Kocsis, B., Tremaine, S., 2011,
"Resonant relaxation and the warp of the stellar disc in the Galactic
Centre," Monthly Notices of the Royal Astronomical Society,
3.

Observations of the spatial distribution and kinematics of
young stars in the Galactic Centre can be interpreted as showing that the stars
occupy one, or possibly two, discs of radii .0.05-0.5 pc. The most prominent
("clockwise") disc exhibits a strong warp: the normals to the mean
orbital planes in the inner and the outer third of the disc differ by .60°.
Using an analytical model based on Laplace-Lagrange theory, we show that such
warps arise naturally and inevitably through vector resonant relaxation between
the disc and the surrounding old stellar cluster.

The operation of plate tectonics on Earth is essential to
modulate its atmospheric composition over geological time and is thus commonly
believed to be vital for planetary habitability at large. It has been suggested
that plate tectonics is very likely for super-Earths, with or without surface
water, because a planet with a larger mass tends to have sufficient convective
stress to escape from the mode of stagnant-lid convection. Here, this
suggestion is revisited on the basis of the recently developed scaling laws of
plate-tectonic convection, which indicate that the planetary size plays a
rather minor role and that the likelihood of plate tectonics is controlled
largely by the presence of surface water.

Context. The CoRoT
satellite has recently discovered a hot Jupiter that transits across the disc
of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days.

Aims: We model the photospheric activity of the star and use
the maps of the active regions to study stellar differential rotation and the
star-planet interaction.

Methods: We apply a maximum entropy spot model to fit the
optical modulation as observed by CoRoT during a uninterrupted interval of ~
140 days. Photospheric active regions are assumed to consist of spots and
faculae in a fixed proportion with solar-like contrasts.

Results: Individual active regions have lifetimes up to
30-40 days. Most of them form and decay within five active longitudes whose
different migration rates are attributed to the stellar differential rotation
for which a lower limit of DW/W = 0.12 ± 0.02 is obtained. Several active regions show a
maximum of activity at a longitude lagging the subplanetary point by ~ 200°
with the probability of a chance occurrence being smaller than 1 percent.

Conclusions: Our spot modelling indicates that the
photospheric activity of CoRoT-6 could be partially modulated by some kind of
star-planet magnetic interaction, while an interaction related to tides is
highly unlikely because of the weakness of the tidal force.

This paper reports Very Large Array observations at 325 and
1425 MHz (l90 cm and l 20 cm) during and near the
periastron passage of HD 80606b on HJD 2454424.86 (2007 November 20). We obtain
flux density limits (3s) of 1.7 mJy and 48 mJy at 325 and 1425 MHz, respectively, equivalent to
planetary luminosity limits of 2.3 ×1024 erg s-1and 2.7
×1023 erg s-1. Unfortunately, these are several orders
of magnitude above the nominal Jovian value (at 40 MHz) of 2 ×1018
erg s-1. The motivation for these observations was that the
planetary magnetospheric emission is driven by a stellar wind-planetary
magnetosphere interaction so that the planetary luminosity would be elevated
near periastron. We estimate that, near periastron, HD 80606b might be as much
as 3000 times more luminous than Jupiter. Recent transit observations of HD
80606b provide reasonably stringent constraints on the planetary mass and
radius, and, because of the planet's highly eccentric orbit, its rotation
period is likely to be "pseudo-synchronized" to its orbital period,
allowing a robust estimate of the former. Consequently, we are able to make
relatively robust estimates of the emission frequency of the planetary
magnetospheric emission and find it to be around 60-90 MHz. While this is too
low for our reported observations, we compare HD 80606b to other high-eccentricity
systems and assess the detection possibilities for both near-term and more
distant future systems. Of the known high-eccentricity planets, only HD 80606b
is likely to be detectable, as the others (HD 20782B and HD 4113) are both
lower mass and longer rotational periods, which imply weaker magnetic field
strengths. We find that both the forthcoming "EVLA low band" system,
which will operate as low as 65 MHz, and the Low Frequency Array may be able to
improve upon our planetary luminosity limits for HD 80606b, and do so at a more
optimum frequency. If the low-frequency component of the Square Kilometre Array
(SKA-lo) and a future lunar radio array are able to approach their thermal
noise limits, they should be able to detect an HD 80606b-like planet, unless
the amount by which the planet's luminosity increases is substantially less
than the factor of 3000 that we estimate; for the SKA-lo, which is to be
located in the southern hemisphere, future planetary surveys will have to find
southern hemisphere equivalents of HD 80606b.

In this paper, we investigate the atmospheric excitation of
polar motion (PM) associated with the El Niñouthern Oscillation (ENSO) phenomenon. ENSO effects on length-of-day due to
changes in the axial component of atmospheric angular momentum (AAM) have long been recognized, but
identification of PM excitation with ENSO-induced equatorial AAM anomalies has proved more elusive.
Here we use an appropriately modified form of the inverted barometer (IB)
assumption to study ENSO-related atmospheric torques arising from pressure loading
on the Earth's ellipsoidal bulge and mountains and from frictional wind stress
over the Earth's land- and ocean-covered surface. The resulting dissipation
torques, which accommodate adjustment of the oceanic mass distribution to
time-variable atmospheric loading, are found to be small. The ellipsoidal
torques have the largest amplitude, reflecting the order-of-magnitude
discrepancy between the height departures of the Earth's bulge (~20 km) and its
surface orography (~2 km). Because of relatively uniform pressure covariances
with the Southern Oscillation Index over the continents for the largely
land-based X component and the uniform IB response for the largely ocean-based
Y component; however, the ENSO-related PM excitation arising from the ellipsoidal torques
is reduced to an amplitude comparable with the sum of regional mountain torques
from the individual continents. The largest of these are generated over Asia and Antarctica, arising from efficient coupling of
ENSO-related surface pressure anomalies
with large-scale orographic features. The geometrical mitigation of the
ellipsoidal torques, classically expected to dominate equatorial AAM forcing, accounts for the lack of a
detectable atmosphere-driven polar motion response to ENSO.

High-contrast near-infrared imaging of the nearby star HR
8799 has shown three giant planets. Such images were possible because of the
wide orbits (>25astronomical units, where 1AU is the Earth-Sun distance) and
youth (<100Myr) of the imaged planets, which are still hot and bright as
they radiate away gravitational energy acquired during their formation. An
important area of contention in the exoplanet community is whether outer
planets (>10AU) more massive than Jupiter form by way of one-step
gravitational instabilities or, rather, through a two-step process involving
accretion of a core followed by accumulation of a massive outer envelope
composed primarily of hydrogen and helium. Here we report the presence of a
fourth planet, interior to and of about the same mass as the other three. The
system, with this additional planet, represents a challenge for current planet
formation models as none of them can explain the in situ formation of all four
planets. With its four young giant planets and known cold/warm debris belts,
the HR 8799 planetary system is a unique laboratory in which to study the
formation and evolution of giant planets at wide (>10AU) separations.

Recent discoveries of several transiting planets with
clearly non-zero eccentricities and some large obliquities started changing the
simple picture of close-in planets having circular and well-aligned orbits. The
two major scenarios that form such close-in planets are planet migration in a
disk and planet-planet interactions combined with tidal dissipation. The former
scenario can naturally produce a circular and low-obliquity orbit, while the
latter implicitly assumes an initially highly eccentric and possibly
high-obliquity orbit, which are then circularized and aligned via tidal
dissipation. Most of these close-in planets experience orbital decay all the
way to the Roche limit as previous studies showed. We investigate the tidal
evolution of transiting planets on eccentric orbits, and find that there are
two characteristic evolution paths for them, depending on the relative
efficiency of tidal dissipation inside the star and the planet. Our study shows
that each of these paths may correspond to migration and scattering scenarios.
We further point out that the current observations may be consistent with the
scattering scenario, where the circularization of an initially eccentric orbit
occurs before the orbital decay primarily due to tidal dissipation in the
planet, while the alignment of the stellar spin and orbit normal occurs on a
similar timescale to the orbital decay largely due to dissipation in the star.
We also find that even when the stellar spin-orbit misalignment is observed to
be small at present, some systems could have had a highly misaligned orbit in
the past, if their evolution is dominated by tidal dissipation in the star.
Finally, we also re-examine the recent claim by Levrard et al. that all
orbital and spin parameters, including eccentricity and stellar obliquity,
evolve on a similar timescale to orbital decay. This counterintuitive result
turns out to have been caused by a typo in their numerical code. Solving the
correct set of tidal equations, we find that the eccentricity behaves as
expected, with orbits usually circularizing rapidly compared to the orbital
decay rate.

We report the discovery of a transiting planet orbiting the
star TYC 6446-326-1. The star, WASP-22, is a
moderately bright (V = 12.0) solar-type star (Teff= 6000 ± 100 K,
[Fe/H] = -0.05 ± 0.08). The light curve of the star obtained with the
WASP-South instrument shows periodic transit-like features with a depth of
about 1% and a duration of 0.14 days. The presence of a transit-like feature in
the light curve is confirmed using z-band photometry obtained with Faulkes
Telescope South. High-resolution spectroscopy obtained with the CORALIE and
HARPS spectrographs confirms the presence of a planetary mass companion with an
orbital period of 3.533 days in a near-circular orbit. From a combined analysis
of the spectroscopic and photometric data assuming that the star is a typical
main-sequence star we estimate that the planet has a mass M P= 0.56
± 0.02M Jup and a radius R P= 1.12 ± 0.04RJup.
In addition, there is a linear trend of 40 m s-1yr-1in
the radial velocities measured over 16 months, from which we infer the presence
of a third body with a long-period orbit in this system. The companion may be a
low mass M-dwarf, a white dwarf, or a second planet.

We carry out a resolution study on the
fragmentation boundary of self-gravitating discs. We perform three-dimensional
Smoothed Particle Hydrodynamics simulations of discs to determine whether the
critical value of the cooling time-scale in units of the orbital time-scale, bcrit, converges with increasing
resolution. Using particle numbers ranging from 31 250 to 16 million (the
highest resolution simulations to date) we do not find convergence. Instead,
fragmentation occurs for longer cooling time-scales as the resolution is
increased. These results suggest that at the very least, the critical value of
the cooling time-scale is longer than previously thought. However, the absence
of convergence also raises the question of whether or not a critical value
exists. In light of these results, we caution against using cooling time-scale
or gravitational stress arguments to deduce whether gravitational instability
may or may not have been the formation mechanism for observed planetary
systems.

A high level of diversity has already
been observed among the planets of our own Solar System. As such, one expects
extrasolar planets to present a wide range of distinctive features, therefore
the characterisation of Earth- and super Earth-like planets is becoming of key
importance in scientific research. The S earch ( Spectropolarimetric Exoplanet
Atmosphe Re CHaracerisation) mission proposal of this paper represents one
possible approach to realising these objectives. The mission goals of S earch
include the detailed characterisation of a wide variety of exoplanets, ranging
from terrestrial planets to gas giants. More specifically, S earch will
determine atmospheric properties such as cloud coverage, surface pressure and
atmospheric composition, and may also be capable of identifying basic surface
features. To resolve a planet with a semi major axis of down to 1.4 AU and 30
pc distant S earch will have a mirror system consisting of two segments, with
elliptical rim, cut out of a parabolic mirror. This will yield an effective
diameter of 9 m along one axis. A phase mask coronagraph along with an integral
spectrograph will be used to overcome the contrast ratio of star to planet light.
Such a mission would provide invaluable data on the diversity present in
extrasolar planetary systems and much more could be learned from the
similarities and differences compared to our own Solar System. This would allow
our theories of planetary formation, atmospheric accretion and evolution to be
tested, and our understanding of regions such as the outer limit of the
Habitable Zone to be further improved.

Context. Astronomical research dealing with accurate radial
velocity measurements need reliable astronomical standards to calibrate the
spectrographs and to assess possible systematics. Stellar radial velocity
standards offer a reference at the level of a few hundred m s-1and
are not adequate for most present needs.

Aims: We aim to show that sunlight reflected by asteroids is
a fairly accessible way to record a high-resolution solar spectrum from the
whole disk, which can therefore be used as a radial velocity standard and can
improve the uncertainties of solar line positions.

Methods: We used solar light reflected by the asteroid Ceres
observed with HARPS to measure solar lines' wavelengths.

Results: We provide a new solar atlas with 491 line
wavelengths in the range 540-690 nm and 222 lines in the range 400-410 nm
obtained from reflected solar spectrum of Ceres. These measurements are
consistent with those of Allende Prieto & Garcia Lopez (1998b) based on FTS solar atlases but with a factor 3
higher precision.

Conclusions: This atlas provides a benchmark for wavelength
calibration to check radial velocity accuracy down to 44 m s-1locally
and a few m s-1globally. The asteroid-based technique could provide
a new way to track radial velocity shifts with solar activity cycle, as well as
to derive convective shifts suitable for comparison with theoretical
atmospheric models. It could also be used to study radial velocity deviations
in spectrographs such as those recently detected in HIRES and UVES. Dedicated
HARPS observations of other asteroids could improve present results
substantially and these investigations have been solicited. Full Table 2 is
only available in electronic form at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/525/A74

Most extrasolar planets currently known were discovered by
means of an indirect method that measures the stellar wobble caused by the
planet. We previously studied a triple system composed of a star and a nearby
binary on circular coplanar orbits. We showed that although the effect of the
binary on the star can be differentiated from the stellar wobble caused by a
planet, because of observational limitations the two effects may often remain
indistinguishable. Here, we develop a model that applies to eccentric and
inclined orbits. We show that the binary's effect is more likely to be mistaken
by planet(s) in the case of coplanar motion observed equator-on. Moreover, when
the orbits are eccentric, the magnitude of the binary's effect may be larger
than in the circular case. Additionally, an eccentric binary can mimic two
planets with orbital periods in the ratio 2/1. However, when the star's orbit
around the binary's center of mass has a high eccentricity and a reasonably
well-constrained period, it should be easier to distinguish the binary's effect
from a planet.

Context. Near-Earth asteroid 162173 (1999 JU3) is a
potential flyby and rendezvous target for interplanetary missions because of
its easy-to-reach orbit. The physical and thermal properties of the asteroid
are relevant for establishing the scientific mission goals and also important
in the context of near-Earth object studies in general.

Methods: With three sets of published thermal observations
(ground-based N-band, Akari IRC, Spitzer IRS), we applied a thermophysical model
to derive the radiometric properties of the asteroid. The calculations were
performed for the full range of possible shape and spin-vector solutions
derived from the available sample of visual lightcurve observations.

Results: The near-Earth asteroid 162173 (1999 JU3) has an
effective diameter of 0.87 ± 0.03 km and a geometric albedo of 0.070 ± 0.006.
The c2-test reveals a strong preference
for a retrograde sense of rotation with a spin-axis orientation of lecl = 73°, becl = -62° and Psid = 7.63 ±
0.01 h. The most likely thermal inertia ranges between 200 and 600 J m-2s-0.5
K-1, about a factor of 2 lower than the value for 25143 Itokawa.
This indicates that the surface lies somewhere between a thick-dust regolith
and a rock/boulder/cm-sized, gravel-dominated surface like that of 25143
Itokawa. Our analysis represents the first time that shape and spin-vector
information has been derived from a combined data set of visual lightcurves
(reflected light) and mid-infrared photometry and spectroscopy (thermal
emission).

Rapid
geomagnetic fluctuations with periods less than a couple of years, so called
geomagnetic jerks, are coincident with sharp changes in rate of change of
Earth's length of day (LOD) and phase of the Chandler wobble. Here I examine the
rotational variations in response to sudden changes of toroidal core surface
flows for geomagnetic jerks, assuming rigid rotation of the outer core and core
surface flows at both boundaries (CMB and ICB) with the magnitude of ~3
km yr-1. I take into account the gravitational torque acting on the
inner core associated with convective processes in the mantle and the
electromagnetic (EM) coupling for a model with conductivity of the core of 5 ×105 S m-1and a 200 m conducting layer of 5 ×105
S m-1at the bottom of the mantle. The present study indicates that
rapid accelerations of the flow at the CMB can produce LOD change consistent with observed LOD derivative with ~0.1 ms yr-1,
but do not produce much for the polar motion. On the other hand, rapid
accelerations of the flow at the ICB insignificantly affect the LOD change, but can produce polar
motion signals that might affect the Chandler wobble if we adopt the EM
coupling for a model with the flows of ~3 km yr-1and
root-mean-square value of 4~5 mT for the radial magnetic field at the ICB.

Angular momentum transport and accretion in protoplanetary
discs are generally believed to be driven by magnetohydrodynamics (MHD)
turbulence via the magnetorotational instability (MRI). The dynamics of solid bodies
embedded in such discs (dust grains, boulders, planetesimals and planets) may
be strongly affected by the turbulence, such that the formation pathways for
planetary systems are determined in part by the strength and spatial
distribution of the turbulent flow. We examine the dynamics of planetesimals,
with radii between 1m and 10 km, embedded in turbulent protoplanetary discs,
using 3D MHD simulations. The planetesimals experience gas drag and stochastic
gravitational forces due to the turbulent disc. We use, and compare the results
from, local shearing box simulations and global models in this study. The main
aims of this work are to examine: the growth, and possible saturation, of the
velocity dispersion of embedded planetesimals as a function of their size and
disc parameters; the rate of radial migration and diffusion of planetesimals;
the conditions under which the results from shearing box and global simulations
agree. We find good agreement between local and global simulations when
shearing boxes of dimension 4H ×16H ×2H are used (H being the local scale height).
The magnitude of the density fluctuations obtained is sensitive to the box
size, due to the excitation and propagation of spiral density waves. This
affects the stochastic forcing experienced by planetesimals. The correlation
time associated with the stochastic forcing is also found to be a function of
the box size and aspect ratio. The equilibrium radial velocity dispersion, s(vr), obtained depends on
the radii, RP, of the planetesimals. Bodies with RP= 50m
achieve the smallest value with s(vr) ~= 20ms-1. Smaller bodies
are tightly coupled to the gas, and boulders with RP = 1m attain a
value of s(vr)
similar to the turbulent velocity of the gas (~100ms-1). Equilibrium
values of s(vr)
for bodies larger than 100m are not achieved in our simulations, but in all
models we find rapid growth of the velocity dispersion for planetesimals of
size 1 and 10km, such that s(vr) >= 160ms-1after a run time of
1200 orbits at a distance of 5au from the central star. These values are too
large to allow for the runaway growth of planetesimals, and mutual collisions
would lead to catastrophic disruption. Radial migration due to gas drag is
observed for bodies with RP~= 1m, and is only modestly affected by
the turbulence. Larger bodies undergo a random walk in their semimajor axes,
leading to radial diffusion through the disc. For our fiducial disc model, we
estimate that radial diffusion across a distance of ~=2.5au would occur for
typical planetesimals in a swarm located at 5au over a disc lifetime of 5Myr.
Radial diffusion of this magnitude appears to be inconsistent with Solar system
constraints. Our models show that fully developed magnetohydrodynamics (MHD)
turbulence in protoplanetary discs would have a destructive effect on embedded
planetesimals. Relatively low levels of turbulence are required for traditional
models of planetesimal accretion to operate, this being consistent with the
existence of a dead zone in protoplanetary discs.

Noordam, J.E., Smirnov, O.M., 2010,
"The MeqTrees software system and its use for third-generation calibration
of radio interferometers," Astronomy and Astrophysics,524,
61.

Context. The formulation of the radio interferometer
measurement equation (RIME) for a generic radio telescope by Hamaker et al.
has provided us with an elegant mathematical apparatus for better
understanding, simulation and calibration of existing and future instruments.
The calibration of the new radio telescopes (LOFAR, SKA) would be unthinkable
without the RIME formalism, and new software to exploit it.

Aims: The MeqTrees software system is designed to implement
numerical models, and to solve for arbitrary subsets of their parameters. It
may be applied to many problems, but was originally geared towards implementing
Measurement Equations in radio astronomy for the purposes of simulation and
calibration. The technical goal of MeqTrees is to provide a tool for rapid
implementation of such models, while offering performance comparable to
hand-written code. We are also pursuing the wider goal of increasing the rate
of evolution of radio astronomical software, by offering a tool that
facilitates rapid experimentation, and exchange of ideas (and scripts).

Methods: MeqTrees is implemented as a Python-based front-end
called the meqbrowser, and an efficient (C++-based) computational back-end
called the meqserver. Numerical models are defined on the front-end via a
Python-based Tree Definition Language (TDL), then rapidly executed on the
back-end. The use of TDL facilitates an extremely short turn-around time (hours
rather than weeks or months) for experimentation with new ideas. This is also
helped by unprecedented visualization capabilities for all final and
intermediate results. A flexible data model and a number of important
optimizations in the back-end ensures that the numerical performance is
comparable to that of hand-written code.

Results: MeqTrees is already widely used as the simulation
tool for new instruments (LOFAR, SKA) and technologies (focal plane arrays). It
has demonstrated that it can achieve a noise-limited dynamic range in excess of
a million, on WSRT data. It is the only package that is specifically designed
to handle what we propose to call third-generation calibration (3GC), which is
needed for the new generation of giant radio telescopes, but can also improve
the calibration of existing instruments.

We present observations of three
distinct transits of HD 17156b obtained with the Fine Guidance Sensors on board
the Hubble Space Telescope. We analyzed both the transit photometry and
previously published radial velocities to find the planet-star radius ratio RP/Rêspan>= 0.07454 ± 0.00035, inclination i =
86.49+0.24.0.20 deg, and scaled semimajor axis a/ Rêspan>= 23.19+0.32.0.27. This
last value translates directly to a mean stellar density determination êspan>= 0.522+0.021.0.018
g cm.3. Analysis of asteroseismology observations by the companion
paper of Gilliland et al. provides a consistent but significantly
refined measurement of rêspan>= 0.5308 ± 0.0040. We compare stellar
isochrones to this density estimate and find Mêspan>= 1.275 ± 0.018 M Sun and a stellar
age of 3.37+0.20.0.47 Gyr. Using this estimate of Mêspan>and incorporating the density constraint from
asteroseismology, we model both the photometry and published radial velocities
to estimate the planet radius RP= 1.0870 ± 0.0066 RJand
the stellar radius Rêspan>= 1.5007 ± 0.0076 R Sun. The planet
radius is larger than that found in previous studies and consistent with
theoretical models of a solar-composition gas giant of the same mass and
equilibrium temperature. For the three transits, we determine the times of
mid-transit to a precision of 6.2 s, 7.6 s, and 6.9 s, and the transit times
for HD 17156 do not show any significant departures from a constant period. The
joint analysis of transit photometry and asteroseismology presages similar
studies that will be enabled by the NASA Kepler Mission.

This paper gives an analytic proof of the existence of
Schubart-like orbit, a periodic orbit with singularities in the symmetric
collinear four-body problem. In each period of the Schubart-like orbit, there
is a binary collision (BC) between the inner two bodies and a simultaneous
binary collision (SBC) of the two clusters on both sides of the origin. The
system is regularized and the existence is proved by using a "turning
point" technique and a continuity argument on differential equations of
the regularized Hamiltonian.

By studying multiple
extrasolar planetary systems, it is possible to obtain constraints for
planetary masses and orbital inclinations using the detection of mutual
perturbations. An analysis of precise radial velocity measurements might reveal
these planet-planet interactions and yield a more accurate view of such planetary
systems. As in generic data modelling problems, a fit to radial velocity data
series has a set of unknown parameters of which parametric derivatives have to
be known by both the regression methods and the estimations for the
uncertainties. In this paper, an algorithm is described that aids the
computation of such derivatives when planetary perturbations are not neglected.
The application of the algorithm is demonstrated for the planetary systems of
HD 73526, HD 128311 and HD 155358. In addition to the functions related to
radial velocity analysis, the actual implementation of the algorithm contains
functions that compute spatial coordinates, velocities and barycentric
coordinates for each planet. These functions aid the joint analysis of multiple
transiting planetary systems, transit timing and/or duration variations or
systems where the proper motion of the host star is also measured involving
high precision astrometry. The practical implementation related to the
above-mentioned problems features functions that make these types of
investigation simple and effective.

We present a new study of the evolution of the Carina dwarf
galaxy that includes a simultaneous derivation of its orbit and star formation
history. The structure of the galaxy is constrained through orbital parameters derived
from the observed distance, proper motions, radial velocity, and star formation
history. The different orbits admitted by the large proper motion errors are
investigated in relation to the tidal force exerted by an external potential
representing the Milky Way. Our analysis is performed with the aid of fully
consistent N-body simulations that are able to follow the dynamics and the
stellar evolution of the dwarf system in order to determine the star formation
history of Carina self-consistently. We also find a star formation history
characterized by several bursts, partially matching the observational
expectation. We find also compatible results between dynamical projected
quantities and the observational constraints. The possibility of a past interaction
between Carina and the Magellanic Clouds is also separately considered and
deemed unlikely. Appendices are only available in electronic form at
http://www.aanda.org

Context. Nulling interferometry in the mid-IR using two
telescopes (commonly referred to a Bracewell interferometer) is one possible
way of directly detecting exoplanets in the habitable zone and their
characterisation in terms of possible life signatures. A large wavelength
domain is needed to simultaneously detect the infrared spectral features of a
set of a bio-tracers. An achromatic phase shift of p is then required, and we previously
presented a new concept for such a function that allows a simple design with
only one device per beam. It is based on two cellular mirrors, called the
chessboards, where each cell has a thickness that introduces, for any given
central wavelength, a phase shift of (2k + 1) p or of 2kp on the fraction of the wave it
reflects.

Aims: We explore a
more rigorous way to establish the optimum cell pattern design to attain the
best theoretical performances for planet detection over a broad wavelength
range. Two possible types of interferometers are now considered: on-axis and
multi-axis.

Methods: We derived a rather simple iterative scheme for both
designs, determining the thickness and XY position of the cells. The method
confers to the chessboards a high degree of internal symmetry. Each design can
be described as an iterative Bracewell interferometer characterised by an
integer order. We demonstrate that their efficiencies increases with the power
of that order.

Results: The device acts both spatially and versus
wavelengths as an optical differential operator on the 3D light distribution.
Its power is best understood in the on-axis case since its effect is to push
away the stellar light from the centre over a very broad range of wavelengths,
leaving space for an out of phase object to appear in the cleaned central
region. We explore the theoretical performances for on-axis and multi-axis designs
in the parameter space, and we especially compute the rejection factor for
starlight and the attenuation factor for planet light and introduce the
relative nulling efficiency metric. We show that, even with some realistic
piston error added, the performances could meet the Darwin space project specifications for
both designs, i.e., cancellation of the starlight by a factor of 105
over a wavelength range of 6-17 mm.

The Flexible Image Transport System (FITS) has been used by
astronomers for over 30 years as a data interchange and archiving format; FITS
files are now handled by a wide range of astronomical software packages. Since
the FITS format definition document (the .standard.) was last printed in this
journal in 2001, several new features have been developed and standardized,
notably support for 64-bit integers in images and tables, variable-length
arrays in tables, and new world coordinate system conventions which provide a
mapping from an element in a data array to a physical coordinate on the sky or
within a spectrum. The FITS Working Group of the International Astronomical
Union has therefore produced this new version 3.0 of the FITS standard, which
is provided here in its entirety. In addition to describing the new features in
FITS, numerous editorial changes were made to the previous version to clarify
and reorganize many of the sections. Also included are some appendices which
are not formally part of the standard. The FITS standard is likely to undergo
further evolution, in which case the latest version may be found on the FITS
Support Office Web site at http://fits.gsfc.nasa.gov/, which also provides many
links to FITS-related resources.

Context. Empirical evidence suggests a tantalizing but
unproven link between various indicators of solar activity and the barycentric
motion of the Sun. The latter is exemplified by transitions between regular and
more disordered motion modulated by the motions of the giant planets, and rare
periods of retrograde motion with negative orbital angular momentum. An
examination of the barycentric motion of exoplanet host stars, and their
stellar activity cycles, has the potential of proving or disproving the Sun's
motion as an underlying factor in the complex patterns of short- and long-term
solar variability indices, by establishing whether such correlations exist in
other planetary systems. In either case, these studies may lead to further
insight into the nature of the solar dynamo.

Aims: Some 40 multiple exoplanet systems are now known, all
with reasonably accurate orbital elements. The forms and dynamical functions of
the barycentric motion of their host stars are examined. These results can be
compared with long-term activity indicators of exoplanet host stars, as they
become available, to examine whether the correlations claimed for the Sun also
exist in other systems.

Methods: Published orbital elements of multiple exoplanetary
systems are used to examine their host star barycentric motions. For each system,
we determine analytically the orbital angular momentum of the host star, and
its rate of change.

Results: A variety of complex patterns of barycentric
motions of exoplanet host stars is demonstrated, depending on the number,
masses and orbits of the planets. Each of the behavioural types proposed to
correlate with solar activity are also evident in exoplanet host stars:
repetitive patterns influenced by massive multiple planets, epochs of rapid
change in orbital angular momentum, and intervals of negative orbital angular
momentum.

Conclusions: The study provides the basis for independent
investigations of the widely-studied but unproven suggestion that the Sun's
motion is somehow linked to various indicators of solar activity. We show that,
because of the nature of their barycentric motions, the host stars HD 168443
and HD 74156 offer particularly powerful tests of this hypothesis.

Two new companions to the Pluto-Charon binary system have
been detected in 2005 by Weaver et al. These small satellites, named Nix
and Hydra, are located beyond Charon's orbit. Although they are small when
compared to Charon, their gravitational perturbations can decrease the
stability of the external region (beyond Charon's orbit). The dynamical structure
of this external region is analysed by numerically simulating a sample of
particles under the gravitational effects of Pluto, Charon, Nix and Hydra. As
expected the effects of Nix and Hydra decrease the external stable region.
Agglomerates of particles can survive even after 105 orbital periods
of the binary in some regions, such as coorbital to Nix and Hydra and between
their orbits. We also analysed the effects of hypothetical satellites on the
orbital evolution of Nix and Hydra in order to constrain an upper limit size.
Some hypothetical satellites can be coorbital to Nix or Hydra without provoking
any significant gravitational effects on them.

Many small moonlets that create propeller structures have
been found in Saturn's rings by the Cassini spacecraft. We study the dynamical
evolution of such 20-50 m sized bodies, which are embedded in Saturn's rings.
We estimate the importance of various interaction processes with the ring
particles on the moonlet's eccentricity and semi-major axis analytically. For
low ring surface densities, the main effects on the evolution of the
eccentricity and the semi-major axis are found to be caused by collisions and
the gravitational interaction with particles in the vicinity of the moonlet.
For high surface densities, the gravitational interaction with self-gravity
wakes becomes important. We also perform realistic three-dimensional,
collisional N-body simulations with up to a quarter of a million particles. A
new set of pseudo shear periodic boundary conditions is used, which reduces the
computational costs by an order of magnitude compared to previous studies. Our
analytic estimates are confirmed to within a factor of two. On short timescales
the evolution is always dominated by stochastic effects caused by collisions
and gravitational interaction with self-gravitating ring particles. These
result in a random walk of the moonlet's semi-major axis. The eccentricity of
the moonlet quickly reaches an equilibrium value owing to collisional damping.
The average change in semi-major axis of the moonlet after 100 orbital periods
is 10-100m. This translates to an offset in the azimuthal direction of several
hundred kilometres. We expect that such a shift is easily observable. Two
movies are only available in electronic form at http://www.aanda.org

Context. TMR-1C is a candidate protoplanet that lies at a
separation of about 10. (~1000 AU) from the Class I protobinary TMR-1 (IRAS 04361+2547) located in the
Taurus molecular cloud. A narrow filament-like structure was observed in the
discovery HST/NICMOS images, extending southeast from the central proto-binary
system towards TMR-1C, suggesting a morphology in which the candidate
protoplanet may have been ejected from the TMR-1 system. Follow-up low-resolution
spectroscopy, however, could not confirm if this object is a protoplanet or a
low-luminosity background star

Aims: We present two epochs of near-infrared photometric
observations obtained at the CFHT of TMR-1C. The time span of ~7 years
between the two sets of observations provides an opportunity to (a) check for
any photometric variability similar to that observed among young stellar
objects, which would indicate the youth of this source, and to (b) determine
the proper motion.

Results: TMR-1C displays large photometric variability between 1
and 2 mag in both the H- and K<SUB>s</SUB>-bands. From our 2002
observations, we find a (H-Ks) color of 0.3 mag, which is much bluer
than the value of 1.3 mag reported by T98 from HST observations. Also, we
observe brightening in both the H- and Ks-bands when the colors are
bluer; i.e., the object gets redder as it becomes fainter. We have
explored the possible origins for the observed variability, and find extinction
due to the presence of circumstellar material to be the most likely scenario.
The observed large-amplitude photometric variations and the possible presence
of a circumstellar disk are strong arguments against this object being an old
background star.

In view of the
assumption that any planetary system is likely to be composed of more than one
planet, and that a multiple planet system with a large-mass planet has a
greater chance of detailed follow-up observations, the multiple planet system
may be an efficient way to search for sub-Jovian planets. We study the central
region of the magnification pattern for the triple lens system composed of a star,
a Jovian mass planet and a low-mass planet to answer the question of if the
low-mass planet can be detected in high-magnification events. We compare the
magnification pattern of the triple lens system with that of a best-fitted
binary system composed of a star and a Jovian mass planet, and check the
probability of detecting the low-mass secondary planet whose signature will be
superposed on that of the primary Jovian mass planet. Detection probabilities
of the low-mass planet in the triple lens system are quite similar to the
probability of detecting such a low-mass planet in a binary system with a star
and only a low-mass planet, which shows that the signature of a low-mass planet
can be effectively detected even when it is concurrent with the signature of
the more massive planet, implying that the binary superposition approximation
works over a relatively broad range of planet mass ratio and separations, and
the inaccuracies thereof do not significantly affect the detection probability
of the lower-mass secondary planet. Since the signature of the Jovian mass
planet will be larger and lasting longer, thereby warranting more intensive
follow-up observations, the actual detection rate of the low-mass planet in a
triple system with a Jovian mass can be significantly higher than that in a
binary system with a low-mass planet only. We conclude that it may be
worthwhile to develop an efficient algorithm to search for `super-Earth'
planets in the paradigm of the triple lens model for high-magnification
microlensing events.

We have acquired submillimeter observations of 33 fields
containing 37 Herbig Ae/Be (HAEBE) stars or potential HAEBE stars, including
SCUBA maps of all but two of these stars. Nine target stars show extended dust
emission. The other 18 are unresolved, suggesting that the dust envelopes or
disks around these stars are less than a few arcseconds in angular size. In
several cases, we find that the strongest submillimeter emission originates
from younger, heavily embedded sources rather than from the HAEBE star, which
means that previous models must be viewed with caution. These new data, in
combination with far-infrared flux measurements available in the literature,
yield spectral energy distributions (SEDs) from far-infrared to millimeter
wavelengths for all the observed objects. Isothermal fits to these SEDs
demonstrate excellent fits, in most cases, to the flux densities longward of
100 mm. We find
that a smaller proportion of B-type stars than A- and F-type stars are
surrounded by circumstellar disks, suggesting that disks around B stars
dissipate on shorter timescales than those around later spectral types. Our
models also reveal that the mass of the circumstellar material and the value of
b are
correlated, with low masses corresponding to low values of b. Since low values of b imply large grain sizes, our
results suggest that a large fraction of the mass in low- b sources is locked up in very large
grains. Several of the isolated HAEBE stars have disks with very flat
submillimeter SEDs. These disks may be on the verge of forming planetary
systems.

Shannon, R.M., Cordes, J.M., 2010,
"Assessing the Role of Spin Noise in the Precision Timing of Millisecond
Pulsars," The Astrophysical Journal,725, 1607-1619.

We investigate rotational spin noise (referred to as timing
noise) in non-accreting pulsars: millisecond pulsars, canonical pulsars, and
magnetars. Particular attention is placed on quantifying the strength and
non-stationarity of timing noise in millisecond pulsars because the long-term
stability of these objects is required to detect nanohertz gravitational
radiation. We show that a single scaling law is sufficient to characterize
timing noise in millisecond and canonical pulsars while the same scaling law
underestimates the levels of timing noise in magnetars. The scaling law, along
with a detailed study of the millisecond pulsar B1937+21, leads us to conclude
that timing noise is latent in most millisecond pulsars and will be measurable
in many objects when better arrival time estimates are obtained over long data
spans. The sensitivity of a pulsar timing array to gravitational radiation is
strongly affected by any timing noise. We conclude that detection of proposed
gravitational wave backgrounds will require the analysis of more objects than
previously suggested over data spans that depend on the spectra of both the
gravitational wave background and of the timing noise. It is imperative to find
additional millisecond pulsars in current and future surveys in order to reduce
the effects of timing noise.

This study investigates the nonlinear stability of the
triangular equilibrium points when the bigger primary is an oblate spheroid and
the infinitesimal body varies (decreases) it's mass in accordance with Jeans'
law. It is found that these points are stable for all mass ratios in the range
of linear stability except for three mass ratios depending upon oblateness
coefficient A and b, a constant due to the variation in mass governed by Jeans' law.

We present and discuss five candidate
exoplanetary systems identified with the Kepler spacecraft. These five systems
show transits from multiple exoplanet candidates. Should these objects prove to
be planetary in nature, then these five systems open new opportunities for the
field of exoplanets and provide new insights into the formation and dynamical
evolution of planetary systems. We discuss the methods used to identify
multiple transiting objects from the Kepler photometry as well as the
false-positive rejection methods that have been applied to these data. One
system shows transits from three distinct objects while the remaining four
systems show transits from two objects. Three systems have planet candidates
that are near mean motion commensurabilities.two near 2:1 and one just outside
5:2. We discuss the implications that multi-transiting systems have on the
distribution of orbital inclinations in planetary systems, and hence their
dynamical histories, as well as their likely masses and chemical compositions.
A Monte
Carlo
study indicates that, with additional data, most of these systems should
exhibit detectable transit timing variations (TTVs) due to gravitational
interactions, though none are apparent in these data. We also discuss new
challenges that arise in TTV analyses due to the presence of more than two planets in a
system.

We combine nulling
interferometry at 10 mm using the MMT and Keck Telescopes with spectroscopy, imaging, and
photometry from 3 to 100 mm using Spitzer to study the debris disk around b Leo over a broad range of spatial
scales, corresponding to radii of 0.1 to ~100 AU. We have also measured the
close binary star o Leo with both Keck and MMT interferometers to verify our
procedures with these instruments. The b Leo debris system has a complex structure: (1)
relatively little material within 1 AU (2) an inner component with a color
temperature of ~600 K, fitted by a dusty ring from about 2-3 AU and (3) a
second component with a color temperature of ~120 K fitted by a broad dusty
emission zone extending from about ~5 AU to ~55 AU. Unlike many other A-type stars
with debris disks, b Leo lacks a dominant outer belt near 100 AU.

The realisation and maintenance of a Galileo Terrestrial
Reference Frame (GTRF) is the main function of the Galileo Geodetic Service
Provider (GGSP). The GTRF shall be compatible with the latest International
Terrestrial Reference Frame (ITRF) within a precision level of 3 cm (2 sigma).
The connection to the ITRF is realized and validated by stations of the
International GNSS Service (IGS) and by geodetic local ties to stations equipped with
other geodetic techniques. It is demonstrated that this GTRF can be maintained
by including the Galileo Signal-in-Space data, once Galileo reaches its
operational stage.The GGSP will also provide additional products, such as Earth
Rotation Parameters, satellites orbits, clock corrections for satellites and
stations, which will be offered to the Galileo user community to have most
precise access to the GTRF and will be used to monitor the accuracy of the
corresponding Galileo Mission Segment.The GGSP was built up in time, and for a
final demonstration the full system was operated for an interval of 6 months.
During that time also microwave data from the two active GIOVE satellites were
used.The GGSP Consortium followed the most up to date IGS standards of weekly
processing during seven monthly campaigns (November 2006 to June 2008) and a
continuous processing from September 2008 to February 2009 delivering several
versions of the GTRF. The latest GTRF solution (GTRF09v01) has an RMS position
difference with respect to the ITRF2005 computed over the 71 common stations of
1.1 and 2.9 mm in the horizontal and vertical components, respectively. The RMS
velocity differences are 0.3 and 0.6 mm/y, respectively. The GGSP GPS satellite orbits and clock
corrections agree with the IGS Final products at a level of 5.11 mm and
0.02.0.03 ns, respectively.The quality of the GIOVE orbits is at a level of
20.30 cm. The Hydrogen-Maser on board of GIOVE-B is nearly one order of
magnitude better than the GPS satellite clocks.

Context. Debris disc analysis and modelling provide crucial
information about the structure and the processes at play in extrasolar
planetary systems. In binary systems, this issue is more complex because the
disc should also respond to the companion star's perturbations.

Aims: We explore the dynamical evolution of a collisionally
active debris disc for different initial parent body populations, diverse
binary configurations, and optical depths. We focus on the radial extent and
size distribution of the disc in a stationary state.

Methods: We numerically followed the evolution of 105
massless small grains, initially produced from a circumprimary disc of parent
bodies following a size distribution in dN µ s-3.5ds . Grains were
submitted to both stars' gravity and radiation pressure. In addition, particles
were assigned an empirically derived collisional lifetime.

Results: For all the binary configurations, the disc extends
far beyond the critical semi-major axis acrit for orbital stability.
This is due to the steady production of small grains, placed by radiation
pressure on eccentric orbits reaching beyond acrit . The amount of
matter beyond acrit depends on the balance between collisional
production and dynamical removal rates: it increases for more massive discs, as
well as for eccentric binaries. Another important effect is that, in the
dynamically stable region, the disc is depleted from its smallest grains. Both
results could lead to observable signatures.

Conclusions: We have shown that a companion star can never
fully truncate a collisionally active disc. For eccentric companions, grains in
the unstable regions can contribute significantly to the thermal emission in
the mid-IR. Discs with sharp outer edges, especially bright ones such as
HR4796A, are probably shaped by other mechanisms.

One of the persistent complications in searches for
transiting exoplanets is the low percentage of the detected candidates that
ultimately prove to be planets, which significantly increases the load on the
telescopes used for the follow-up observations to confirm or reject candidates.
Several attempts have been made at creating techniques that can pare down
candidate lists without the need of additional observations. Some of these
techniques involve a detailed analysis of light curve characteristics; others
estimate the stellar density or some proxy thereof. In this paper, we extend
upon this second approach, exploring the use of independently calculated
stellar densities to identify the most promising transiting exoplanet
candidates. We use a set of CoRoT candidates and the set of known transiting
exoplanets to examine the potential of this approach. In particular, we note
the possibilities inherent in the high-precision photometry from space
missions, which can detect stellar asteroseismic pulsations from which accurate
stellar densities can be extracted without additional observations.

Light curves from the Kepler Mission contain valuable
information on the nature of the phenomena producing the transit-like signals.
To assist in exploring the possibility that they are due to an astrophysical
false positive, we describe a procedure (BLENDER) to model the photometry in
terms of a "blend" rather than a planet orbiting a star. A blend may
consist of a background or foreground eclipsing binary (or star-planet pair)
whose eclipses are attenuated by the light of the candidate and possibly other
stars within the photometric aperture. We apply BLENDER to the case of Kepler-9
(KIC 3323887), a target harboring two previously confirmed Saturn-size planets
(Kepler-9 b and Kepler-9 c) showing transit timing variations, and an
additional shallower signal with a 1.59 day period suggesting the presence of a
super-Earth-size planet. Using BLENDER together with constraints from other
follow-up observations we are able to rule out all blends for the two deeper
signals and provide independent validation of their planetary nature. For the
shallower signal, we rule out a large fraction of the false positives that
might mimic the transits. The false alarm rate for remaining blends depends in
part (and inversely) on the unknown frequency of small-size planets. Based on
several realistic estimates of this frequency, we conclude with very high
confidence that this small signal is due to a super-Earth-size planet (Kepler-9
d) in a multiple system, rather than a false positive. The radius is determined
to be 1.64+0.19.0.14 REarth and current spectroscopic
observations are as yet insufficient to establish its mass.

Context. Several competing scenarios for planetary-system
formation and evolution seek to explain how hot Jupiters came to be so close to
their parent stars. Most planetary parameters evolve with time, making it hard
to distinguish between models. The obliquity of an orbit with respect to the
stellar rotation axis is thought to be more stable than other parameters such
as eccentricity. Most planets, to date, appear aligned with the stellar
rotation axis; the few misaligned planets so far detected are massive (> 2 MJ).

Aims: Our goal is to measure the degree of alignment between
planetary orbits and stellar spin axes, to search for potential correlations
with eccentricity or other planetary parameters and to measure long term radial
velocity variability indicating the presence of other bodies in the system.

Methods: For
transiting planets, the Rossiter-McLaughlin effect allows the measurement of
the sky-projected angle b between the stellar rotation axis and a planet's orbital axis. Using
the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six
transiting hot Jupiters found by the WASP consortium. We combine these with
long term radial velocity measurements obtained with CORALIE. We used a
combined analysis of photometry and radial velocities, fitting model parameters
with the Markov Chain Monte Carlo method. After obtaining b we attempt to statistically
determine the distribution of the real spin-orbit angle y.

Results: We found that three of our targets have b above 90°: WASP-2b: b = 153°+11-15,
WASP-15b: b = 139.6°+5.2-4.3
and WASP-17b: b = 148.5°+5.1-4.2; the other three (WASP-4b,
WASP-5b and WASP-18b) have angles compatible with 0°. We find no dependence
between the misaligned angle and planet mass nor with any other planetary
parameter. All six orbits are close to circular, with only one firm detection
of eccentricity e = 0.00848+0.00085-0.00095 in WASP-18b.
No long-term radial acceleration was detected for any of the targets. Combining
all previous 20 measurements of b and our six and transforming them into a
distribution of y we find that between about 45 and 85% of hot Jupiters have y > 30°.

Conclusions: Most hot Jupiters are misaligned, with a large
variety of spin-orbit angles. We find observations and predictions using the
Kozai mechanism match well. If these observational facts are confirmed in the
future, we may then conclude that most hot Jupiters are formed from a dynamical
and tidal origin without the necessity to use type I or II migration. At
present, standard disc migration cannot explain the observations without
invoking at least another additional process. Using observations with the high
resolution éelle spectrograph HARPS mounted on the ESO 3.6 m (under proposals
072.C-0488, 082.C-0040 & 283.C-5017), and with the high resolution éelle
spectrograph CORALIE on the 1.2 m Euler Swiss Telescope, both installed at the
ESO La Silla Observatory in Chile.RV data is only available at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/524/A25

The Euler Commission of the SwissAcademy of Sciences intends to terminate
the edition of Leonhard Euler's works in the next year 2011 after nearly one
hundred years since the beginning of the editorial works. These works include,
e.g., Volume 3 of the Series quarta A which will contain the correspondence
between Leonhard Euler (1707-1783) and Daniel Bernoulli (1700-1783) and which
is currently being edited by Dr. Emil A. Fellmann (Basel) and Prof. Dr. Gleb K. Mikhailov (Moscow). This correspondence contains more
than hundred letters, principally from Daniel Bernoulli to Euler. Parts of this
correspondence were published uncommented already in 1843. It is astonishing
that, apart from mathematics and physics (mainly mechanics and hydrodynamics),
many topics addressed concern astronomy. The major part of the preserved
correspondence between Euler and Daniel Bernoulli, in which astronomical themes
are discussed, concerns celestial mechanics as the dominant discipline of
theoretical astronomy of the eighteenth century. It was triggered and coined
mainly by the prize questions of the Paris Academy of Science. In more than two
thirds of the letters current problems and questions concerning celestial
mechanics of that time are treated, focusing on the lunar theory and the great
inequality in the motions of Jupiter and Saturn as special applications of the
three body problem. In the remaining letters, problems concerning spherical
astronomy are solved and attempts are made to explain certain phenomena in the
field of "cosmic physics" concerning astronomical observations.

In this paper, we derive the analytical solution of a
satellite orbit disturbed by atmospheric drag. The disturbance force vector is
first transformed and rotated to the orbital frame so that it can be used in
the simplified Gaussian equations of satellite motion. Then, the force vector
is expanded to triangular functions of the Keplerian angular elements and the
disturbances are separated into three parts: short-periodic terms with
triangular functions of M, long-periodic terms with triangular functions of (w, i) and secular terms [non-periodic
functions of (a, e)] with a program using mathematical symbolic operation
software. The integrations are then carried out with respect to M, (w, i) and t, respectively, to obtain
the analytical solutions of satellite orbits disturbed by atmospheric drag.
Some interesting conclusions are obtained theoretically. The atmospheric
disturbance force is not a function of W. The semimajor axis a of the orbital ellipse is
reduced in a constant and strong manner by the air disturbance; the shape of
the ellipse (eccentricity e) changes towards a more circular orbit in a linear
and weak manner. The right ascension of the ascending node W and the mean anomaly M are
influenced by the disturbance only short periodically.

In this paper, we derive to the second order (5 ×10-6)
the analytical solution of a satellite orbit disturbed by the lunar
gravitational force. The force vector is first expanded to omit terms smaller
than the third order (10-9). Then, four terms of potential functions
are derived from the expanded force vector and set into the Lagrangian
equations of satellite motion to obtain the theoretical solutions. For the
first term of the potential functions, the solutions are derived directly. For
the second term, mathematical expansions and transformations are used to
separate disturbances into three parts: short-periodic terms with triangular
functions of M, long-periodic terms with triangular functions of (w, i, W) and secular terms with
non-periodic functions of (a, e). The integrations are then carried out with
respect to M, (w, i, W) and t, to
obtain the analytical solutions of satellite orbits with a program using
mathematical symbolic operation software. The third potential function differs
from the second by a factor and the fourth is simpler than the second.
Therefore, the solutions are derived similarly using slightly modified
programs, respectively. The results show that only two Keplerian elements (w, M) are linearly perturbed by lunar
gravitation; that is, the lunar attracting force will cause a linear regression
(delay) of the perigee (orientation of the ellipse) and a linear delay of the
position (mean anomaly) on an Earth satellite. The Keplerian element a
(semimajor axis of the ellipse) is not perturbed long periodically as the
others. The derived solutions are also valid for solar and planetary
gravitational disturbances. Because of the distance differences between the
Moon, the Sun and the planets to the Earth or an Earth satellite, the solutions
are of third and fourth orders for solar and planetary gravitational disturbances
on an Earth satellite, respectively.

We provide a detailed statistical study of the ejection of
fictitious Earth-mass planets from the habitable zones of the solar twins HD
20782 and HD 188015. These systems possess a giant planet that crosses into the
stellar habitable zone, thus effectively thwarting the possibility of habitable
terrestrial planets. In the case of HD 188015, the orbit of the giant planet is
essentially circular, whereas in the case of HD 20782, it is extremely
elliptical. As starting positions for the giant planets, we consider both the
apogee and perigee positions, whereas the starting positions of the Earth-mass
planets are widely varied. For the giant planets, we consider models based on
their minimum masses as well as models where the masses are increased by 30%.
Our simulations indicate a large range of statistical properties concerning the
ejection of the Earth-mass planets from the stellar habitable zones. For
example, it is found that the ejection times for the Earth-mass planets from
the habitable zones of HD 20782 and HD 188015, originally placed at the centre
of the habitable zones, vary by a factor of ~200 and ~1500, respectively,
depending on the starting positions of the giant and terrestrial planets. If
the mass of the giant planet is increased by 30%, the variation in ejection
time for HD 188015 increases to a factor of ~6000. However, the short survival
times of any Earth-mass planets in these systems are of no surprise. It is
noteworthy, however, that considerable differences in the survival times of the
Earth-mass planets are found, which may be relevant for establishing guidelines
of stability for systems with less intrusive giant planets.